As critical dimensions of complementary metal-oxide-semiconductor (CMOS) transistors continuously decrease, total powers consumed by the CMOS transistors continuously increase, because short channel effects (e.g., an increased leakage current) becomes more and more serious. Supply voltages cannot continuously decrease as the critical dimensions of the CMOS transistors decrease. A subthreshold swing of the typical CMOS transistor has a limited value of about 60 mV/decade, and a certain amount of change in the voltage becomes necessary to change the CMOS transistors from an off state to an on state. Correspondingly, typical CMOS transistors have a minimum supply voltage.
Compared to the CMOS transistors, a tunneling field effect transistor (TFET) has a subthreshold swing smaller than 60 mV/decade. Correspondingly, the TFET has a smaller working voltage and a smaller leakage current. The TFET gradually substitutes CMOS transistor and has a wide application in the low-power-consumption devices.
Among TFETs, a vertical tunneling field-effect transistor (VTFET) has a tunable length of a vertical tunnel and a tunable width of the gate (for example, a change in the width of the gate could affect a saturating current through the vertical tunnel).
However, the performance of conventionally fabricated VTFET devices still needs to be improved. The disclosed devices and methods are directed to at least partially alleviate one or more problems set forth above and to solve other problems in the art.